problem solving strategies for compacted soils · compacted soils dr. susan d. day ... technique:...
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ProblemSolvingStrategies forCompacted Soils
Dr.SusanD.DayForest Resources &Environmental Conservation, Virginia Tech
• Understanding Compacted Soil Syndrome• When doyouact?
• Q&A• Strategiesand Tradeoffs• Technique: SPR• Implications forStormwater• MoreQ&A
BriefAgenda
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UnderstandingCompacted SoilSyndrome
AmericanElms
Worcester,Mass.1912
The fallbacksolution
Photo: P.EricWiseman
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Photo:RobertLlewellyn—Magnoliaacuminata (CucumberTree)TheRemarkableTrees ofVirginia
SustainableLandDevelopment?
Primefarmland soilwasgraded down3ft toredirectstormwater tobioinfiltration swale
At“peak”timeofyear(May)3yearslater, treedieback,thinturf,thincanopies,nutrientdeficiencies
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Compactedsoilsyndrome
Photo:RachelM.Layman
• At5-10cmmacroaggregates werereducedby44%
• Lost35%oftotalsoilorganiccarbon(0-10cm)• Lost47%ofmineral-boundcarbon• Subsurfacedrainagereducedfromabout3”anhourtolessthan½”anhour.
Photo: Jeannette E.Spaghetti (CC)
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Whataboutplants?
wetres=0.6MPa
moistres=1.75MPa
dryres=2.0MPa
SilverMapleatThreeLevelsofSoilStrength
Ascompaction increases
14-yearoldTilia tomentosa inasiltyclayloam(Day&Amateis2009)
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Sugarmapleroots
viewedthrough arhizotronwindow
Whendoyouact?—Determininganaction
threshold
Soil compactionMeasure bybulkdensityorpenetrationresistance
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Youcan’tinterpretsoilbulkdensitywithoutsoiltexture
Bulkdensity=1.4g•cm-3
sandyloam—noworriessiltyclayloam—watchout
Daddow andWarrington1983
%SAND
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Let’stakeaquestionbreak
StrategiesandTradeoffs
Blended andEngineered Soils
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Missing Soil?
DarrenDeStefanoUSTaxCourt
RecycledSoils
Photo:JayBanks
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Photo: Jeannette E.Spaghetti (CC)
Rehabilitating SoilinPlace
TECHNIQUE: SOILPROFILEREBUILDING
Remediates SoilCompaction
SetsSoil Formation Processes inGear
Increases Ksat, soil C, andtree growth
Specs areavailable online
Peer-reviewed science
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WillnotcorrectyoursoilpHproblems
Notforusearoundlargetrees
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Will reducecompaction,increase tree growth,improvepermeability, increase soilcarbonstores,andset long-term soilformationprocesses ontrack
Photo: Jeannette E.Spaghetti (CC)
Apply4inchesofcomposttograded subsoil
Soil ProfileRebuilding—Arehabilitationtechnique
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Backhoe to2ft,scoopupanddroptocreatecompostveins to2ft.
• Return topsoil asusual (4”min.)andtill 8”• Plant treesorother woody veg• Treatsurface toreduce erosion andmaintain
infiltration
8 cm
33cm
53 cm
18 cm
1.51
1.77
1.76
1.91(9mos)1.76(5yrs)
LowResistance(Topsoil)
HighResistance(Compactedsubsoil)
MediumResistance(Subsoil)
TypicalPractice
LoamSoil—SoilBulkDensityg/cm3
1.28
1.75
1.69
1.35 (9mos)1.49(5yrs)
ProfileRebuilding
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AdaptationofDaddow andWarrington,1983bySustainableSitesInitiative
Soil inTreeRootZone
Without Rehabyr 1=1.91gcm-3
WithRehabyr 1=1.35gcm-3
Without Rehabyr 5=1.76gcm-3
With Rehabyr 5=1.49gcm-3
CanopyAreaapproximatelydoubledafter7yearsincontrolled experiments
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CanopyAreainm2
Arlington County StreetMedians
DavidMitchell,2014
Implications forStormwater
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Site-level Effects SubsurfacePermeability 10-40cm(Ksat)
AgriculturalSoil—4to5cm/hrComparetoHSG B
Simplegrading,urbanlanddevelopment—1to2cm/hrComparetoHSG CorD
Rehabilitatedsoil—10to11cm/hrComparetoHSG AorB
Chenetal. ScienceoftheTotalEnvironment2014.
Urbanlanddevelopment
SoilManagement
Ksat
Atypicalsurfacetreatmentsforresearchpurposesresult inrestrictedflow
Bottleneckin“typicaldevelopedland”hasrapidwaterflow
Aggregate-associatedC
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Theurbanforestsystem
ComplexityoftheLandscape
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Chen, Y.,Day,S. D.,Shrestha, R.K.,Strahm, B.D.,Wiseman, P.E.,2014. Influenceofurban landdevelopment andsoil rehabilitation onsoil–atmospheregreenhouse gas fluxes.Geoderma 226,348-353.
Chen, Y.,Day,S. D.,Wick, A.F.,McGuire, K.J. ,2014. Influence ofurban landdevelopment andsubsequent soil rehabilitation onsoil aggregates, carbon, andhydraulic conductivity.Science of theTotal Environment.494–495, 329-336.
Chen, Y.,Day,S. D.,Wick, A.F., Strahm,B.D.,Wiseman, P.E.,Daniels, W.L.,2013.Changes in soil carbonpools andmicrobial biomass fromurban landdevelopment andsubsequent post-development soil rehabilitation. Soil BiologyandBiochemistry 66, 38-44.
Layman,R.M.,Day.S.D.,Mitchell, D.K.,Chen, Y.,Harris, J.R.,Daniels, W.L.2015.Below ground matters: Urbansoil rehabilitation increases treecanopyandspeeds establishment. Under review atUrban Forestry &Urban Greening
JournalArticlesforSPR
urbanforestry.frec.vt.edu
Wantmoreinfo?
• RecentArticleCityTrees(Sept/Oct)
• DownloadSpecificationsurbanforestry.frec.vt.edu/SRES
• Detailsunderproduction
THANKYOU
Collaborators:J. R.Harris,JosephDove,QingfuXiao,E.G.McPherson,N.Bassuk,BrianStrahm,AbbeyWick,W.LeeDaniels,P.EricWiseman,KevinMcGuire,Tess(Wynn)Thompson,andVincentVerweij
GraduateStudents:RachelLayman,YujuanChen,JuliaBartens,andDavidMitchell
SoilProfileRebuildingSpecificationsavailableaturbanforestry.frec.vt.edu/SRES
Partial supportprovidedbytheUSDA-ForestServiceNationalUrbanandCommunityForestryAdvisoryCouncil,TreeResearch&EducationFund,theInstituteforCriticalTechnologyandAppliedScienceatVirginia Tech,andtheUSDA’sMcIntire-Stennisprogram
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Photo: Peter Nijenhuis (CC)
Let’stalksomemoreaboutsoil!
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